There is food processing apparatus of the type broadly set forth above having a working bowl or vessel with a motor-driven shaft projecting vertically upwards through the bottom of the bowl on which various selected rotary tools can be engaged to be driven by the shaft for performing various food processing operations as may be desired by the user. For further information about this type of food processing apparatus, the reader may refer to U.S. Pat. No. 3,892,365--Pierre Verdun, and to my prior U.S. Pat. No. 3,985,304.
In this apparatus, there is used a removable cutter tool having a plurality of thin rigid cutter blades secured to a hollow hub and extending outwardly from the hub. When the user installs this removable tool, its hollow hub slides vertically down around the motor-driven shaft. In order to provide a driving connection between the shaft and this hollow hub, the shaft is provided with axially extending driving coupling means, such as a flat face keyway or splines, or a square, or hexagonal shape may be provided to achieve the positive driving relationship. The hollow hub has complementary coupling means, such as internal lugs, keys, longitudinally extending relative to the length of the shaft for engaging the driving coupling means operatively associated with the rotatable drive shaft. One of these blades in the normal operating position of this cutter tool is positioned near the bottom of the working bowl along the length of the blade with a small spacing between the bottom of the bowl and this blade.
In this type of food processing apparatus, the rotary cutter tool may be driven at a speed in the range from approximately 750 revolutions per minute (R.P.M.) to 2,000 R.P.M. This rotary cutter tool may be used for different kinds of food processing, for example, for cutting or mincing meat, for cutting vegetables of all kinds, including condiments and for working and preparing doughs and pastes. Even a relatively small quantity of food material can be processed, if desired, because of the small spacing between the lower horizontal blade and the horizontal bottom of the working bowl, when the tool is in its normal operating position. The tool can also be used for preparing mayonnaise, or any other similar emulsion, because the lower blade is closely spaced to the bottom, thereby providing a highly effective shearing, emulsifying action when the cutter tool is in its normal operating position. Moreover, when shelled peanuts, or shelled cashew nuts, or other shelled nuts, are placed into the working bowl, the rotary cutter tool can process these nuts into peanut butter or cashew butter or other nut butter.
However, in making such nut butter, using the prior art apparatus, it has been my observation that the mass of partially chopped or pulverized nuts may tend to collect in the bottom of the bowl. The undesired result is that the lower blade sometimes tends to "ride up" or climb while moving like a hydrofoil rapidly through the mass of pulverulent food material. The clearance between the lower revolving blade and the bowl bottom progressively increases until this blade is skimming or skipping along over the upper surface of the food material. This is a dynamically stable state, wherein the lower blade is seen skimming at high velocity over a substantially undisturbed bed of chopped or pulverized nuts upon which it is moving. Once the cutter tool has ridden up into this dynamically stable lifted position, it will continue in that elevated location until the machine is shut off and the food material is manually pushed aside, so that the cutter can resume its normal down position fully seated relative to the drive shaft.
This failure of such prior art apparatus to complete the processing of shelled nuts into nut butter could unexpectedly occur any time. My experimental trials have shown that these unexpected conditions of the blade lift and climbing action up onto the top surface of the food mass are more likely to occur when there is only a modest quantity of nuts in the bowl bottom.
U.S. Pat. No. 3,493,022--Jean Mantelet does not state whether or not the mincing machine described therein can actually be used to process shelled nuts into nut butter. This Mantelet patent was cited during the prosecution of the Verdun patent mentioned above, and it is discussed herein in case the reader might consider it to be pertinent prior art. In the Mantelet mincing machine, the coupling between the blade-carrier hub and the driving spindle is produced by means of inclined ramps or fins wrought on the lateral surface of the spindle on which are engaged with a clearance correspondingly inclined grooves wrought in the lateral surface of a central bore of the hub. The inclination of these fins and grooves is selected, as specified by Mantelet, such that one rotation of the spindle in its normal direction of rotation tends to engage the fins in the grooves, that is to say, to draw the hub downwards. These inclined ramps or fins are said to provide an automatic engagement of the hub on the spindle as soon as the appliance is started and to ensure that the hub cannot fly off during operation in any case. Such inclined ramps or fins require a difficult manipulation of the tool during its installation or removal and thus is entirely different from the present invention in which the slicing blade itself dynamically produces a "negative lift" to hold the readily removable cutter tool in place on the drive shaft.
In U.S. Pat. No. 3,612,125--Hulmut Krauth, the upper exposed end of the rotatable output shaft of the motor is screw threaded, and a suitable nut is threaded onto this upper end, so as to maintain the sleeve-shaped carrier of the cutter blades in place. The use of such a fastening nut is time consuming for the user. Moreover, it tends to be unsanitary because food particles can lodge in the crevices between the nut and the exposed threaded end of the output shaft. Thus, this Krauth patent is entirely different from the present invention in which the slicing blade itself dynamically produces a negative lift to hold the readily removable cutter tool in place on its drive shaft.